Analysis of pattern features

ABSTRACT

The embodiments disclose a method for an electron curing reverse-tone process, including depositing an etch-resistant layer onto a patterned imprinted resist layer fabricated onto a hard mask layer deposited onto a substrate, curing the etch-resistant layer using an electron beam dose during etching processes of imprinted pattern features into the hard mask and into the substrate and using analytical processes to quantify reduced pattern feature placement drift errors and to quantify increased pattern feature size uniformity of imprinted pattern features etched.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on U.S. Provisional Patent Application Ser.No. 61/672,271 filed: Jul. 16, 2012, entitled “Electron CuringReverse-Tone Process”, by Zhaoning Yu.

BACKGROUND

Imprint resists are mainly designed to optimize their feature fillingand release properties; they usually do not provide sufficientmechanical stability and etch resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an overview of an electron curingreverse-tone process of one embodiment.

FIG. 2 shows a block diagram of an overview flow chart of an electroncuring reverse-tone process of one embodiment.

FIG. 3 shows a block diagram of an overview flow chart of a continuationof an electron curing reverse-tone process of one embodiment.

FIG. 4 shows a block diagram of an overview flow chart of a secondcontinuation of an electron curing reverse-tone process of oneembodiment.

FIG. 5A shows for illustrative purposes only an example of spin coatingan etch-resistant layer of one embodiment.

FIG. 5B shows for illustrative purposes only an example of electron beamcuring of etch-resistant material of one embodiment.

FIG. 6A shows for illustrative purposes only an example of resist layerimprinted pattern of one embodiment.

FIG. 6B shows for illustrative purposes only an example of 2-stepreverse-tone etching process of one embodiment.

FIG. 6C shows for illustrative purposes only an example of an electronbeam cured hard mask patterned template of one embodiment.

FIG. 7A shows for illustrative purposes only an example ofetch-resistant layer filled imprinted pattern features of oneembodiment.

FIG. 7B shows for illustrative purposes only an example of electron beamcuring of one embodiment.

FIG. 8 shows for illustrative purposes only an example of a curedstructurally transformed etch-resistant layer material molecule of oneembodiment.

FIG. 9 shows for illustrative purposes only an example of coercivity andsignal amplitude vs. magnetic diameter advantages of the electron curingreverse-tone process of one embodiment.

FIG. 10A shows for illustrative purposes only an example of a controlledpredetermined voltage and dose determination method of one embodiment.

FIG. 10B shows for illustrative purposes only an example of astatistical size and placement distribution quality analysis of oneembodiment.

FIG. 11 shows for illustrative purposes only an example of feature sizedistribution of one embodiment.

FIG. 12 shows for illustrative purposes only an example of evaluatingreverse tone electron beam curing feature placement of one embodiment.

FIG. 13 shows for illustrative purposes only an example of a placementdistribution function of one embodiment.

FIG. 14 shows for illustrative purposes only an example of a placementerror grid of one embodiment.

FIG. 15 shows for illustrative purposes only an example of placementevaluation of one embodiment.

FIG. 16 shows for illustrative purposes only an example of plottedplacement regularity numbers of one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In a following description, reference is made to the accompanyingdrawings, which form a part hereof, and in which is shown by way ofillustration a specific example in which the invention may be practiced.It is to be understood that other embodiments may be utilized andstructural changes may be made without departing from the scope of thepresent invention.

General Overview:

It should be noted that the descriptions that follow, for example, interms of an electron curing a reverse-tone process is described forillustrative purposes and the underlying system may apply to any numberand multiple types of reverse-tone processes.

In an embodiment the fabrication of BPM pattern at various densitiesincluding 250 Gb/in2, 450 Gb/in2, 500 Gb/in2, 1 Tb/in2, 1.5 Tb/in2 and 2Tb/int to 5 Tb/in2 uses a “reverse-tone” process including a wetreverse-tone process, in which a silicon-rich, etch-resistant material(such as HSQ) is deposited including spin-coated on a resist pattern andthen etched back through multi-step reactive ion etching (RIE) to form anegative tone replica of the original.

In some embodiments increasing areal density may cause narrowing of theprocess window feature mechanical instability during etch-back mayincrease dot placement error (the “shifting dots” problem), insufficientetch resistance, and non-homogeneity of resist material at this scaledegrades the dot size uniformity.

FIG. 1 shows a block diagram of an overview of an electron curingreverse-tone process of one embodiment. FIG. 1 shows an electron curingreverse-tone process 100 which begins with a process for examplespin-coating an etch-resistant layer on an imprinted resist patternfabricated on a hard mask layer of a substrate 105.

The etch-resistant layer covers and fills the pattern features of theimprinted resist pattern. A controlled electron beam dose is used forcuring the etch-resistant layer using a controlled electron beam dose110 that structurally transforms the etch-resistant layer material. Thecuring may be done alternatively before or after the spin on glass (SOG)etch-back, the two alternatives lead to different characteristics in theresults, but both increase the pattern quality. The electron beam curingstructural transformation is creating mechanical stability and reducingdrift of etch area and pattern feature position when etching the hardmask material 120. Etching the hard mask material is achieved using a2-step reverse-tone etching process 130. A first predefined etchperforms an etch-back of the electron beam cured etch-resistant layer toexpose the imprinted resist pattern.

A second predefined etch is used for removing the imprinted resist andetching a pattern into the hard mask layer down to the substrate 140.The second predefined etch removes the imprinted resist pattern andforms a negative tone replica of the original pattern. The remainingelectron beam cured etch-resistant layer can be removed creating a hardmask patterned template used for replicating semiconductors and stacksincluding high density bit patterned media (BPM) 150. The removal of theelectron beam cured etch-resistant layer includes using a wet-chemicalprocess such as sodium hydroxide (NaOH). Alternatively the remaining HSQitself is used as part of the mask for the etching of the underlyingstack or semiconductor. Replicating stacks including high density bitpatterned media (BPM) includes using the mask for etching of magneticlayers of stacks by ion beam etching.

DETAILED DESCRIPTION Controlled Electron Beam Curing Process

FIG. 2 shows a block diagram of an overview flow chart of an electroncuring reverse-tone process of one embodiment. FIG. 2 shows a substratewith a hard mask layer deposited thereon 200. A resist layer withimprinted pattern 210 is fabricated on the hard mask layer, establishedfor example by an ultraviolet (UV)-imprint process. A process may beused to descum the imprinted resist layer 220 to reduce the residualresist layer. The descum process removes a portion of the resistmaterial exposing the hard mask layer between pattern features.Alternatively in one embodiment the imprinted resist layer is notdescummed to avoid any potential alterations in the imprinted pattern.An etch-resistant layer 230 including hydrogen silsesquioxane (HSQ) 235is deposited including spin-coated on the imprinted resist pattern 240.

An apparatus is used to cure the etch-resistant layer using electronbeam dose 250 which is controlled to create mechanical stability 252 inthe etch-resistant layer. The mechanical stability will reduce drift ofetch area and pattern feature position 256. The electron beam curingdose is controlled to a predetermined voltage and dose 270 to achieveelectron beam curing 260 of the etch-resistant layer material. Thepredetermined voltage 303 of FIG. 3 may include electron beam irradiatedat an acceleration voltage. The acceleration voltage affects electronpenetration depth. The sample structure in part is used in thedetermination of the predetermined voltage including accelerationvoltages of several hundred volts, 2 kV, 3 kV, 10, 20, 50 and 100 kV.The electron beam curing may cause the hydrogen silsesquioxane (HSQ) tochange from the “cage” structure to a cross-linked “network” structure,shrinks its volume and may increase its density, resulting in a HSQ filmof higher etch resistance and better homogeneity. Description of theprocessing continues in FIG. 3.

First Predefined Etch

FIG. 3 shows a block diagram of an overview flow chart of a continuationof an electron curing reverse-tone process of one embodiment. FIG. 3shows a description processes the continue from FIG. 2 including thecontrolled electron beam irradiation 300 including thermal, ion beam,electron beam, x-ray, photon, ultraviolet (UV), deep ultraviolet (DUV),vacuum ultraviolet (VUV), plasma, microwave, or other types ofirradiation 305.

The controlled electron beam dose uses a predetermined voltage 303 foran acceleration voltage. The electron beam irradiation 300 is used tostructurally transform etch-resistant layer material 310 which reducesvolume 312, increases refractive index N 314 and increases densification316.

In one embodiment curing the etch-resistant layer 320 is performed onthe etch-resistant layer 350. The electron beam irradiation step isadded before a reverse-tone process including a 2-step etch-back andetching. The curing may increase the mechanical stability of the HSQfeatures during the 2-step reverse-tone processing, thus greatlyalleviating the “shifting dots” problem. When the e-beam treatment isperformed before the HSQ etch-back, the process tends to producefeatures with bigger size.

After curing the etch-resistant layer 320 a 2-step reverse-tone etchingprocess 330 is used to etch the hard mask material. A first predefinedetch 340 including reactive ion etching (RIE) 342 usingtetrafluoromethane (CF₄) 346 is used to etch-back cured etch-resistantlayer 360. This embodiment continues as described in FIG. 4.

In another embodiment before the electron beam curing process the firstpredefined etch 340 is used to etch-back the uncured etch-resistantlayer 355.

The electron beam curing 260 of FIG. 2 is used for curing theetch-resistant layer 320 in the etched back etch-resistant layer 380.The 2-step reverse-tone etching process 330 continues as described inFIG. 4.

Second Predefined Etch

FIG. 4 shows a block diagram of an overview flow chart of a secondcontinuation of an electron curing reverse-tone process of oneembodiment. FIG. 4 shows subsequent processing continuing from FIG. 3.The two embodiments of the electron curing reverse-tone process 100processing up to this point both produce electron beam cured and etchedback etch-resistant layer 400. The 2-step reverse-tone etching process330 of FIG. 3 continues with a second predefined etch 410 includingreactive ion etching (RIE) 412 using oxygen gas (O₂) 416.

The second predefined etch 410 performs an etch of a hard mask layer 430and removes the imprinted resist layer 435. This process is etching apattern down to the substrate 440. The electron beam cured and etchedback etch-resistant layer reduces pattern feature placement drift errors442 and increases pattern feature size uniformity 446. The remaining HSQitself can be used as part of the mask for the etching of the underlyingstack or semiconductor. The second predefined etch 410 can alternativelybe followed by a stripping process to remove the etched backetch-resistant layer 450 and forming a negative tone replica of theoriginal pattern.

The etched hard mask including a carbon hard mask layer andalternatively including the etched back electron beam curedetch-resistant layer create a hard mask patterned template 460. In oneembodiment subsequent processes include a substrate ion milled usingpatterned hard mask 465 for patterning of the substrate including a BPMmagnetic stack. The resulting hard mask patterned template 460 may beused for subsequent replication of high-density (>1 Tb/in²) patternedmedia. BPM replicated using the hard mask patterned template produced bythe electron curing reverse-tone process 100 may have 1.5 Tb/in²density, corresponding to a minimum dot-to-dot distance of 22.1 nm. Theelectron curing reverse-tone process 100 increases the quality of thereplicated BPM pattern at >1 Tb/in² density, producing arrays withmarkedly increased dot size at a minimum dot-to-dot distance of 22.1 nm.The hard mask patterned template 460 with reduced pattern featureplacement drift errors and increased pattern feature size uniformity isused for replicating semiconductors 470 and used for replicating stacks480 including high density bit patterned media (BPM) 490. The electroncuring reverse-tone process 100 creates the advantages of placementaccuracy and size uniformity thereby increasing the replicated qualityof semiconductors and stacks.

Spin Coating an Etch-Resistant Layer

FIG. 5A shows for illustrative purposes only an example of spin coatingan etch-resistant layer of one embodiment. FIG. 5A shows a substrate 500with a hard mask layer 510 deposited thereon. The substrate 500 includesmagnetic layers of a stack including a bit patterned media (BPM). Animprinted resist layer 520 on the hard mask layer 510 includes an arrayof one or more imprinted resist pattern feature 528 created using theimprinted pattern 530. Alternatively in one embodiment the imprintedresist layer is not descummed to avoid any potential alterations in theimprinted pattern and an etch-resistant material is deposited onto theresist pattern 540. The etch-resistant material deposition includes spincoating.

A descum process 534 is used to descum the imprinted resist layer 532.The descum process 534 removes excess resist material from each patternfeature 538 and exposes portions of the hard mask layer 510. Anetch-resistant material is deposited onto the resist pattern 540. Anetch-resistant layer material 545 including hydrogen silsesquioxane(HSQ) 235 of FIG. 2 is used to develop mechanical stability and toreduce pattern feature placement drift error and increase patternfeature size uniformity when cured using a controlled dose of electronbeams. Each pattern feature 538 is filled by the etch-resistant layermaterial 545 and which covers the exposed portions of the hard masklayer 510. FIG. 5B describes other processes that follow.

Electron Beam Curing

FIG. 5B shows for illustrative purposes only an example of electron beamcuring of etch-resistant material of one embodiment. FIG. 5B shows acontinuation of processing from FIG. 5A. FIG. 5B shows the substrate500, hard mask layer 510 and examples of the pattern feature 538. Anelectron beam curing of etch-resistant material 550 is performed using acontrolled electron beam dose 555. The controlled electron beam dose 555projects electron beams which flood the etch-resistant layer material545. The controlled electron beam dose 555 structurally transforms themolecules of the etch-resistant layer material 545 to create mechanicalstability.

The 2-step reverse-tone etching process 330 of FIG. 3 uses the firstpredefined etch 340 of FIG. 3 including a reactive ion etching using CF₄565. The reactive ion etching using CF4 565 is used to etch backelectron beam cured etch-resistant material 560. The first predefinedetch 340 of FIG. 3 creates etched back cured etch-resistant material575.

The second predefined etch 410 of FIG. 4 of the 2-step reverse-toneetching process 330 of FIG. 3 including the reactive ion etching usingO₂ 585 is used to etch a hard mask pattern 580. The reactive ion etchingusing O₂ 585 removes the resist material and etches into the hard masklayer 510 down to the substrate 500. Imprint resist is not etchresistant and may not serve as a good mask for some processes. However,it is easier to imprint holes in imprint resist than making resistpillars by the imprint process. A “reverse-tone” process instead ofdirectly using the imprinted resist pattern as a etch mask uses the etchresistance material for example HSQ material to create the mask. Theetched back cured etch-resistant material 575 is used to increasepattern feature placement accuracy and size uniformity. The secondpredefined etch 410 of FIG. 4 produces a patterned hard mask layer 595.The etched etch-resistant material 590 is removed using for example awet-chemical etch including a NaOH solution process and reveals thepatterned hard mask layer 595 on the substrate 500. The removal theetched etch-resistant material 590 for example HSQ prior to IBE of forexample the magnetic stacks may tend to re-deposit the HSQ on the finalproduct during IBE, leaving a layer of unwanted coating.

Alternatively the etched etch-resistant material 590 removal process isnot included where by the remaining etch-resistant material 590 forexample HSQ is used as part of the mask as well. A subsequent processincluding using a RIE process is used to transfer the pattern into anunderlying Si substrate followed by a process to remove the HSQ/carbonmask stack. The patterned hard mask layer 595 on the substrate 500creates a hard mask patterned template 598. The hard mask patternedtemplate 598 is used for used for replicating semiconductors and stacksincluding high density bit patterned media (BPM).

Resist Layer Imprinted Pattern

FIG. 6A shows for illustrative purposes only an example of resist layerimprinted pattern of one embodiment. FIG. 6A shows the substrate 500,deposited hard mask layer 510 and imprinted resist layer 520. Theimprinted pattern 530 creates each imprinted resist pattern feature 528.The descum process 534 is used to descum the imprinted resist layer 532.The descum process 534 removes excess resist from the pattern feature538 and removes resist down to the hard mask layer 510. Alternatively inone embodiment the imprinted resist layer is not descummed to avoid anypotential alterations in the imprinted pattern. Processing continueswherein etch-resistant material is deposited onto the resist pattern540. The etch-resistant layer material 545 covers any exposed surface ofthe hard mask layer 510 and fills each pattern feature 538. Descriptionsof continuing processes are shown in FIG. 6B.

2-Step Reverse-Tone Etching Process

FIG. 6B shows for illustrative purposes only an example of 2-stepreverse-tone etching process of one embodiment. FIG. 6B shows processescontinuing from FIG. 6A. FIG. 6B shows another embodiment of theelectron curing reverse-tone process 100. The substrate 500 has thedeposited hard mask layer 510 upon which are the uncured etch resistantmaterial and descummed patterned resist.

In this embodiment the 2-step reverse-tone etching process 330 of FIG. 3uses the first predefined etch 340 of FIG. 3 before the electron beamcuring process. The first predefined etch 340 of FIG. 3 includes thereactive ion etching using CF₄ 565 used to process an etch-back of theuncured etch-resistant material 600. The reactive ion etching using CF₄565 produces etched back uncured etch-resistant material 620.

The controlled electron beam dose 555 is used for electron beam curingof etched back etch-resistant material 630. The electron beam curingprocess results in etched back cured etch-resistant material 575. Theetched back cured etch-resistant material 575 has structurallytransformed molecules with increased mechanical stability. Descriptionsof subsequent processes are shown in FIG. 6C.

Hard Mask Patterned Template

FIG. 6C shows for illustrative purposes only an example of an electronbeam cured hard mask patterned template of one embodiment. In thisembodiment the 2-step reverse-tone etching process 330 of FIG. 3includes using the second predefined etch 410 of FIG. 4 including thereactive ion etching using O₂ 585 after the electron beam curingprocess. The reactive ion etching using O₂ 585 is used to etch a hardmask pattern 580 down to the substrate 500. The reactive ion etchingusing O₂ 585 removes the imprinted resist layer. The reactive ionetching using O₂ 585 produces a patterned hard mask layer 595. Theetched etch-resistant material 590 is used to increase pattern featureplacement accuracy and size uniformity.

Following the reactive ion etching using O₂ 585, an alternativestripping process is used to remove the etched etch-resistant material587 including a NaOH solution wet-chemical etch 588 removes the etchedetch-resistant material 590. In the alternate the remaining HSQ itselfis used as part of the mask for the etching of the underlying stack orsemiconductor. The patterned hard mask layer 595 on the substrate 500creates the hard mask patterned template 598 used for replicatingsemiconductors 470 of FIG. 4 and used for replicating stacks 480 of FIG.4 including high density bit patterned media (BPM) 490 of FIG. 4.

Etch-Resistant Layer Filled Imprinted Pattern Features

FIG. 7A shows for illustrative purposes only an example ofetch-resistant layer filled imprinted pattern features of oneembodiment. FIG. 7A shows the substrate 500 with the hard mask layer 510deposited thereon. The resist layer with imprinted pattern 210 includesmultiples of an imprinted pattern feature 705 which in this example isan inverted tapered pillar. The etch-resistant layer 230 spin coated onthe imprinted resist covers the resist material. The etch-resistantmaterial including HSQ of an etch-resistant layer fills each imprintedpattern feature 700 of one embodiment.

Electron Beam Curing

FIG. 7B shows for illustrative purposes only an example of electron beamcuring of one embodiment. FIG. 7B shows the substrate 500 with the hardmask layer 510 deposited thereon. An example of an imprinted patternfeature 705 is shown through the etch-resistant layer 230 including HSQis shown as transparent for ease of viewing. The etch-resistant materialhas filled each imprinted pattern feature 705 embedding theetch-resistant material in the resist matrix.

A controlled electron beam emitting apparatus 710 is used to produce forexample flooding electron beams 720 into the etch-resistant layer 230.The flooding electron beams 720 diffuse as they penetrate theetch-resistant material. The controlled electron beam emitting apparatus710 regulates the strength of the emitted electron beams using apredetermined voltage and dose. The predetermined voltage is controlledto enable the flooding electron beams 720 to saturate the volume anddepth of the etch-resistant layer 230 thus curing the etch-resistantmaterials to structurally transform the molecules of the etch-resistantlayer 230.

The etch-resistant layer 230 using HSQ is structurally transformed at acuring dose including ˜1000 μC/cm² to 50,000 μC/cm². The processaffected by the changes in HSQ properties includes the toppling andshifting in HSQ pillars and the strength and adhesion may help thepillars stand including stress vs. strength, and material failure. Themolecular structural transformation reduces volume 312 of FIG. 3,increases refractive index n 314 of FIG. 3 and increases densification316 of FIG. 3 of the etch-resistant layer 230. The transformed electronbeam cured etch-resistant layer 230 has increased mechanical stability.Etching through the cured etch-resistant layer 230 produces reducedpattern feature placement drift error and increased pattern feature sizeuniformity.

Electron Beam Curing Structural Transformation

FIG. 8 shows for illustrative purposes only an example of a curedstructurally transformed etch-resistant layer material molecule of oneembodiment. FIG. 8 shows controlled electron beam dose 555 of FIG. 5Bproduces electron beam curing 260 directed into an uncuredetch-resistant layer material molecule 810. An uncured etch-resistantlayer material molecule of a silicon-rich, etch-resistant materialincluding HSQ has a “cage” or cubic structure. The organic resistmaterial is already cross-linked during the UV-imprint process. Theelectron beam has effects on the imprint resist as well. Ifelectron-beam exposure is done on a UV-cured imprint resist film only,the resist seems first to turn more carbon-like (with increasedrefractive index and reduced thickness). At very high electron beamdoses, the resist film starts to disappear. However, these effects donot render the cured HSQ 2-step reverse-tone process un-workable. Themolecule has silicon (Si) atoms at each corner which are linked byoxygen (O) atoms. A hydrogen (H) atom is attached to each silicon (Si)atom adding to the volume of the molecule.

Each cured structurally transformed etch-resistant layer materialmolecule 820 has a cross-linked “network” structure caused by an atomicredistribution reaction. The etch-resistant layer 545 using for exampleHSQ is structurally transformed at a curing dose of for an example inranges from 1,000 μC/cm² to 50,000 μC/cm². The electron beam curingstructural transformation shrinks the molecule's volume and increasesits density resulting in increased etch resistance. The electron beamcuring increased etch resistance creates mechanical stability preventingpattern feature shifts in position and size degradations during etching.This advantage of electron beam curing produces replications of patternfeature arrays with markedly increased placement accuracy and sizeuniformity increasing the quality of replications for examplesemiconductors and stacks including BPM patterned at >1 Tb/in² density.

Coercivity and Signal Amplitude Vs. Magnetic Diameter

FIG. 9 shows for illustrative purposes only an example of coercivity andsignal amplitude vs. magnetic diameter advantages of the electron curingreverse-tone process of one embodiment. FIG. 9 shows a chart plottingthe coercivity and signal amplitude vs. magnetic diameter 900. The chartshows that signal amplitude increases 910 and coercivity decreases 920as the magnetic diameter [nm] 930 increases. The electron curingreverse-tone process 100 reduces pattern feature placement drift errors442 of FIG. 4 and increases pattern feature size uniformity 446 of FIG.4.

The electron beam curing dose is controlled to a predetermined voltageand dose 270 of FIG. 2 of the electron beams to regulate voltage anddose duration based on type and thicknesses of imprinted resistmaterials, etch-resistant materials, hard mask layer and substrate. Thereduced pattern feature placement drift errors and increased patternfeature size uniformity enables the magnetic diameter [nm] 930 of thepattern features to be optimized, including the maximized magneticdiameter [nm] 930 that produces the least coercivity and most signalamplitude of the substrate magnetic features etched using the hard maskpatterned template 460 of FIG. 4. The pattern features size uniformitynarrows magnetic dots switching field distribution and the patternfeatures placement accuracy reduces “jitter” during signal read-back.

Predetermined Voltage and Dose

FIG. 10A shows for illustrative purposes only an example of a controlledpredetermined voltage and dose determination method of one embodiment.FIG. 10A shows the electron beam curing 260 is controlled to apredetermined voltage and dose 270. Controlled voltage and dose aredetermined by evaluating reverse tone features quality 1000 assures thequality of the products produced. A method for evaluating reverse tonefeatures quality 1010 is used to predetermine the voltage and dose usedin the electron beam curing 260. The evaluation method uses analysis ofelectron beam curing 260 product results, for example bit-patternedmedia (BPM), where statistics can be obtained 1012.

A statistical size and placement distribution quality analysis 1014 isperformed for each statistical analysis reference group 1016. Thestatistical analysis reference group 1016 includes targeted patternfeatures and density 1018, hard mask and substrate layer materials used1020 and electron beam voltage and dose settings 1022. The quality ofthe size of the pattern features and placement of the patterned featuresare analyzed. Patterned features size and placement errors from reversetone process can be separated 1024. The statistical size and placementdistribution analysis 1014 is programmed to evaluate the size andplacement decoupled 1026. One evaluation is a reverse tone feature sizeanalysis 1030 which is described further in FIG. 10B. The otherevaluation is a reverse tone feature placement analysis algorithm 1050described further in FIG. 10B of one embodiment.

Size and Placement Distribution Analysis

FIG. 10B shows for illustrative purposes only an example of astatistical size and placement distribution quality analysis of oneembodiment. FIG. 10B shows the continuation of the descriptions of thestatistical size and placement distribution quality analysis 1014 ofFIG. 10A. The reverse tone feature size analysis 1030 of FIG. 10Aincludes a mean binary (M_(B)) size distribution function 1032. Acalculation of distribution function M_(B) 1034 used in a sizeevaluation 1040. The size evaluation 1040 is used in the assessment ofthe targeted pattern features and density 1018 of FIG. 10A qualityachieved for the electron beam voltage and dose settings 1022 of FIG.10A used on the etch-resistant materials.

FIG. 10B shows a description of the reverse tone feature placementanalysis algorithm 1050 of FIG. 10A which develops one number todescribe placement error 1052. The one number to describe placementerror 1052 is arrived using a mean probability (m_(p)) distributionfunction 1054. A calculation of distribution function m_(p) 1056 isprogrammed wherein random domain templates can be used 1062 with no needto pre-determine the grid 1060. The result of the calculation ofdistribution function m_(p) 1056 quantifies feature placement regularitydescribed by a single parameter 1064. The feature placement regularitydescribed by a single parameter 1064 is used in a placement evaluation1070 to assess of the quality of the targeted pattern features anddensity 1018 of FIG. 10A reached for the electron beam voltage and dosesettings 1022 of FIG. 10A used on the etch-resistant materials. Thejoint results of the size evaluation 1030 and placement evaluation 1070are used to determine voltage and dose resulting in targeted reversetone features quality 1080 of one embodiment.

Feature Size Distribution

FIG. 11 shows for illustrative purposes only an example of feature sizedistribution of one embodiment. FIG. 11 shows the reverse tone featuresize analysis 1030 which uses a sample image for each statisticalanalysis reference group 1100 electron beam curing process resultobtained using a scanning electron microscope (SEM) of one embodiment.

The data collected in the histogram 1110 is an analysis of thebrightness of all the pixels in the original SEM image of the featuresfor example dots. The histogram 1110 distribution (horizontal axis) isfrom 0 to 255 to correspond to a gray scale for example a 256-levelbrightness. The histogram 1110 distribution (horizontal axis) is used toset the brightness “threshold” to turn the original gray-scale (0-255)image into a binary image (0 and 1) that is used to determine a size(brightness) threshold 1120. The threshold 1120 is used as a filter tocreate binary 1130 feature size data from the SEM 1105. The binary 1130is used to create M_(B) 1140 a binary representation of the SEM 1105.The M_(B) 1140 is a filtered and “smoothened” version of the binary 1130through several image processing operations to make the size calculationmore stable. In binary 1130 there are smaller dots near the large dots,these small dots may be interpreted by computer as individual dots,that's why filtering is applied to “smoothen” the binary 1130 image. TheM_(B) 1140 data is shown as a size distribution 1150 which is comparedto a targeted size quality 1160 as a basis for a size evaluation of oneembodiment.

Feature Placement Evaluation

FIG. 12 shows for illustrative purposes only an example of evaluatingreverse tone electron beam curing feature placement of one embodiment.The placement of the features can affect for example ultimate read/writefunctioning quality of the features in for example BPM. FIG. 12 showsalgorithm step 1 1200 used in analyzing feature placement 1210 in thereverse tone feature placement analysis algorithm 1050 of FIG. 10A. TheM_(B) 1140 is used to create M 1230 where M is the same size as theimage MB 1240. M 1230 includes points where the points represent (x_(i),y_(i)) and (x_(i), y_(i)) is the center of a feature, i=1, 2, . . . , N1250. The analysis of M 1230 includes M(x,y)=1 if (x,y)=(x_(i),y_(i)),i=1, 2, . . . N and 0 everywhere else 1260. Additional descriptions ofthe evaluation follow in FIG. 13 of one embodiment.

Placement Distribution Function

FIG. 13 shows for illustrative purposes only an example of a placementdistribution function of one embodiment. FIG. 13 shows the continuationof the process from FIG. 12. An algorithm step 3 1300 is used to performa distribution function 1310. M 1230 has in window m_(i) 1325 showingthe random domain area used in this distribution function 1310. Anenlargement of m_(i) 1325 is shown in m_(i) feature placements 1330.Included in the m_(i) feature placements 1330 is (x_(i),y_(i)) 1335which equals m_(i) 1325 center point coordinates. The collection ofcoordinate points is shown in m_(p) placement data 1340. A calculationdistribution function m_(p) 1350 wherein m_(p) is analogous to a wavefunction ψ(x,y) (in quantum mechanics) 1352. An m_(p) value is theprobability of finding a neighboring feature 1354 for the targetedpattern features and density 1018 of FIG. 10A. A distribution function:m_(p)=(Σ_(i=1) ^(N) m_(i))/N 1360 includes a value for N: total numberof features 1362 and where m_(i)⊂M, centered at (x_(i), y_(i)) 1364. Theplacement distribution process continues and is described further inFIG. 14 of one embodiment.

Placement Error Grid

FIG. 14 shows for illustrative purposes only an example of a placementerror grid of one embodiment. FIG. 14 shows the continuation of theplacement error determination from FIG. 13. FIG. 14 includes algorithmstep 4 1400 used to create a placement error grid 1410. Random domaintemplates can be used 1062 of FIG. 10B where there is no need topre-determine the grid 1060 of FIG. 10B. A peak location determines thegrid 1420 increments and peak width is used to determine placement error1430. The grid 1470 includes the x-y coordinates of “pixels”, the smallsquares in the x-y plane corresponding to the pixels in the originalimage. The grid 1470 includes vertical z-coordinates which are “counts”corresponding to how many neighboring dots are found at the particularpixel location. The x, y and z coordinates are used to create m_(p)1440. The m_(p) 1440 data is used to transition from m_(p) to placementerror 1450 quantification as one number. A placement error relief grid1460 shows a three dimensional (3D) representation of the grid 1470.Additional steps are described in FIG. 15 of one embodiment.

Placement Evaluation

FIG. 15 shows for illustrative purposes only an example of placementevaluation of one embodiment. FIG. 15 shows the continuing process fromFIG. 14 including algorithm step 5 1500. Algorithm step 5 1500 is usedfor placement evaluation 1505 of the images of the random domaintemplates. The images include in this example SEM 1 1510, SEM 2 1520,SEM 3 1530, SEM 4 1540, SEM 5 1550 and SEM 6 1560. Corresponding to theimages are m_(p) 1 1515, m_(p) 2 1525, m_(p) 3 1535, m_(p) 4 1545, m_(p)5 1555 and m_(p) 6 1565. The m_(p) grids show how the placements canvary with different electron beam curing voltage and dose settings. Theevaluations performed are used to determine which settings produce thetargeted results. The further evaluation is described in FIG. 16 of oneembodiment.

Plotted Placement Regularity Number

FIG. 16 shows for illustrative purposes only an example of plottedplacement regularity numbers of one embodiment. FIG. 16 shows acontinuance of the process from FIG. 15 including algorithm step 6 1600.Algorithm step 6 1600 is used to determine each calculated featureplacement error 1610. The calculated feature placement error 1610 isused to determine the probability of finding a neighboring feature 1620.The calculated feature placement error plotting 1630 charts the featureplacement error for each image based on the P_error (nm). The P_error(nm) is one number to describe placement regularity 1660. Each plottedplacement regularity number 1670 for images 1-6 can create a curvedoutput. A P_error curves monotonously when features become irregularlyplaced 1640. The results are used to compare to a targeted placementquality 1650 for the placement evaluation 1070 of FIG. 10B.

The foregoing has described the principles, embodiments and modes ofoperation of the present invention. However, the invention should not beconstrued as being limited to the particular embodiments discussed. Theabove described embodiments should be regarded as illustrative ratherthan restrictive, and it should be appreciated that variations may bemade in those embodiments by workers skilled in the art withoutdeparting from the scope of the present invention as defined by thefollowing claims.

What is claimed is:
 1. A method for an electron curing reverse-toneprocess, comprising: depositing an etch-resistant layer onto a patternedimprinted resist layer fabricated onto a hard mask layer deposited ontoa substrate; curing the etch-resistant layer using an electron beam doseduring etching processes of imprinted pattern features into the hardmask and into the substrate; and using analytical processes to quantifyreduced pattern feature placement drift errors and to quantify increasedpattern feature size uniformity of imprinted pattern features etched. 2.The method of claim 1, wherein the depositing of an etch-resistant layerincludes hydrogen silsesquioxane (HSQ) and is configured to includedeposition processes including spin coating.
 3. The method of claim 1,wherein the electron beam curing is configured to increase mechanicalstability by molecularly transforming etch-resistant layer materialsincluding hydrogen silsesquioxane (HSQ) including material densificationand a reduction in its volume and an increase in its refractive index nto reduce pattern feature placement drift errors and increase patternfeature size uniformity.
 4. The method of claim 1, wherein curingincludes using irradiation including thermal, ion beam, electron beam,x-ray, photon, UV, DUV, VUV, plasma, microwave, or other types ofirradiation controlled to a predetermined energy and dose determinedusing analytical processes to analyze size and placement distribution.5. The method of claim 1, wherein the hard mask layer is patterned usingan etch process including reactive ion etching (RIE) including usingoxygen gas (O₂).
 6. The method of claim 1, wherein etching a patterndown to the substrate using a 2-step reverse-tone etching processincludes a reactive ion etching (RIE) including using Tetrafluoromethane(CF₄) and a reactive ion etching (RIE) including using oxygen gas (O₂).7. The method of claim 1, wherein an etch-back of the curedetch-resistant layer and imprinted resist layer includes using areactive ion etching (RIE) including using Tetrafluoromethane (CF₄). 8.The method of claim 1, wherein the electron curing electron beam dose isperformed before a first reactive ion etching (RIE) and alternativelyperformed after a first reactive ion etching (RIE) and before a secondreactive ion etching (RIE).
 9. The method of claim 1, wherein theelectron curing reverse-tone process can reduce pattern featureplacement drift errors and increase pattern feature size uniformity inprocesses replicating semiconductors and stacks including bit patternedmedia.
 10. An apparatus, comprising: means for curing an etch-resistantlayer deposited onto a pattern imprinted resist layer deposited onto asubstrate with a hard mask layer deposited thereon; means for etchingthe cured pattern imprinted resist layer features into the hard masklayer and substrate; and means for analyzing distributions of placementdrift errors and pattern feature size uniformity of the etched, cured,imprinted, resist layer pattern features.
 11. The apparatus of 10,further comprising means for controlling the electron beam dose curingusing a predetermined voltage and dose of irradiation including thermal,ion beam, electron beam, x-ray, photon, UV, DUV, VUV, plasma, microwave,or other types of irradiation determined using a statistical size andplacement distribution quality analysis.
 12. The apparatus of 10,further comprising means for structurally changing the properties andtransforming etch-resistant layer materials including hydrogensilsesquioxane (HSQ) including material densification, a reduction inits volume and an increase in its refractive index n.
 13. The apparatusof 10, further comprising means for etching the hard mask and substrateusing the 2-step reverse-tone etching process including using a reactiveion etching (RIE) including a first reactive ion etching (RIE) usingTetrafluoromethane (CF₄) and a second reactive ion etching (RIE) usingoxygen gas (O₂).
 14. The apparatus of 10, further comprising means forusing an electron beam dose to cure an etch-resistant layer includeschanging the etch-resistant layer material on a molecular levelincluding causing an atomic redistribution reaction to create across-linked “network” structure.
 15. An electron beam curing process,comprising: using doses of electron beams to cure etch-resistantmaterials deposited onto an pattern imprinted resist layer to createmechanical stability; employing a reverse-tone etching process includingusing etching processes to etch the electron beam cured mechanicallystabilized imprinted resist layer patterned features into a hard masklayer and into a substrate; and using analytical processes topredetermine the electron beam curing doses.
 16. The electron beamcuring process of claim 15, wherein the electron beam curing iscontrolled to regulate voltage and dose based on the type andthicknesses of imprinted resist materials, etch-resistant materials,hard mask layer and substrate and analytical processes results.
 17. Theelectron beam curing process of claim 15, wherein the curing includesirradiation including thermal, ion beam, electron beam, x-ray, photon,UV, DUV, VUV, plasma, microwave, or other types of irradiation used at apredetermined energy and dose determined using a statistical size andplacement distribution quality analysis.
 18. The electron beam curingprocess of claim 15, wherein the hard mask patterned template using a2-step reverse-tone etching process includes using a first etchincluding a reactive ion etching (RIE) using Tetrafluoromethane (CF₄)and using a second etch including reactive ion etching (RIE) usingoxygen gas (O₂).
 19. The electron beam curing process of claim 15,wherein the electron beam curing of the etch-resistant materials createsmechanical stability to reduce pattern feature placement drift errorsand increase pattern feature size uniformity.
 20. The electron beamcuring process of claim 15, wherein the electron beam curing isconfigured to structurally change the properties and transform materialsused for the etch-resistant layer including hydrogen silsesquioxane(HSQ) including material densification, a reduction in its volume and anincrease in its refractive index n.